1. Field of the Invention
The present invention relates to fiber optic information retrieval systems, and more particularly to bar code readers in which light is transmitted through a fiber optic system to a bar code on a package or other piece of retail merchandise or a bar code or other modulated reflective surface as, for example, on a memory tape or disc, and selectively reflected by the bar code back through the system for transmission to a light detector and circuitry to "read" the information contained in the bar code.
2. Description of the Prior Art
A large body of art is developing with regard to the use of fiber optics in bar code reader systems. Bar codes are commonly used to identify inventory items in warehouses and commercial stores. They also may be used in low cost, high memory density paper tape and other storage media. They consist of a number of spaced apart parallel lines of varying widths. Usually dark lines on a light reflecting background are used but reflective lines on a dark background also can be used. Data is coded in the width and spacing of the lines so that when an optical probe is scanned across the code in a direction normal to the lines a light beam in the probe is modulated in a manner which is unique to the particular code. The scanning can be effected either manually or automatically.
The modulated light beam is directed to and detected by an electro-optical detector such as a photodiode or phototransistor. From there the resulting signal is processed and strored in an electronic computer. When used in commercial stores, the computer is programmed to provide the price of the item being read to a cash register terminal and the item is also tallied with the other items read by the bar code reader. Optionally, the price can be manually inserted at the cash register terminal so that the system is not limited to bar code reading.
Generally, optical probes which are used to scan bar codes contain at least two essential components. These are an illuminator and an optical receiver. The illuminator is usually a small incandescent lamp or a light emitting diode (LED) coupled to a lens. The illuminator lens directs the light beam to the surface of the bar code where it is reflected back and collected by the optical receiver. The optical receiver utilizes a second lens to focus the light beam on an electro-optical detector. The light source and light detector may be located adjacent the respective lenses or they may be located remotely and connected to the lenses through optical fibers. The optical fibers are the type often utilized in fiber optic technology and may be made of glass or plastic material. The advantage of using optical fibers is that no electronic components are required inside the probe and thus no electrical connections are required inside the probe. As a result the probe can be smaller and less costly. However, the size, cost and resolving capability of the probes are limited by the need for separate distinct illuminator and receiver channels.
In the prior art, various arrays or systems utilizing plural optical fibers to transmit and receive light have been suggested. For example, Kessler et al in U.S. Pat. No. 3,584,779 and Christie in U.S. Pat. No. 3,671,722 both use two bundles of optical fibers. A color coding system is involved in both of these units, and the light is transmitted through a first bundle from its point of generation to its point of departure from the wand. A portion of the light is reflected back to the wand and is picked up by the fibers in the second bundle. The light is then transmitted through that bundle back to the sensing system. The same type of system is also disclosed in U.S. Pat. Nos. 3,987,278 of Van Elzakker et al, 4,052,594 of Davis, and 4,158,310 of Ho.
Specific shaped arrays of optical fibers have also been suggested. For example Mukai in U.S. Pat. No. 3,937,558 describes several different fiber arrays for the terminal or wand. In one array a large receiving optical fiber is surrounded by a series of small transmitting fibers. A second array has plural rows of individual fibers in which the transmitting and receiving functions are performed by alternate rows of fibers. Mukai also discloses the combination of a plurality of larger receiving fibers surrounded by numerous small transmitting fibers. Weber, on the other hand, in U.S. Pat. No. 3,814,939 discloses a wand having a rectilinear array of rectangular cross-section fibers. The array is manufactured in such a manner that transmisson and reception are effected by alternating fibers.
It has also been suggested that three separate bundles of fibers, each containing plural individual fibers can be utilized. In U.S. Pat. No. 3,766,364 of Krecioch three bundles are utilized. Each bundle contains plural fibers with two of the bundles being utilized for transmission and the third used for reception. Additionally, Pat. No. 3,610,891 of Raciazek discloses individual distinct single fiber transmission and reception lines. Raciazek uses two continuous sensor fibers combined with a single light source fiber positioned between the sensor fibers.
A significantly different system is disclosed by Hartelius in Pat. No. 4,059,338. In this system the light, generated by a laser, is transmitted to a prism which then transmits the light to a flat wide wave guide. The wave guide, which is usually tantalum pentoxide, transmits the light to a unit having pits or indentations. The light striking the pits is reflected and transmitted back through the same wave guide.
All of these units, with the exception of Hartelius, utilize discrete fibers for the transmission and reception functions. This requires careful alignment, and presents problems with regard to the location of the fibers at the end of the wand. Thus it would be a significant improvement in the art to produce a bar code reader which utilizes only a single fiber at the wand. In addition, the above systems generally require the use of lenses to focus the light from the plurality of fibers, or to produce a higher intensity signal for efficient reading of the bar code. Thus elimination of the need for such lenses would be a further improvement.
A simple bar code reader, claimed to be the world's first digital bar code wand, has been announced by Hewlett Packard in "Electronic Design" for Feb. 1, 1980. This wand is said to be capable of scanning black-and-white bar codes and converting the codes to microprocessor-recognizable digital output as a substitute for using a keyboard or push buttons for data entry with an increase in speed of from two to four times by virtue of using bar code scanning. This unit uses a light emitting diode, a photodiode detector, and lenses with appropriate electronic circuitry in the wand. However, it does not use optical fibers and it presents certain problems in attempting to read the finer line bars of standard bar codes.